The present invention concerns insitu detection of tube sagging in semiconductor diffusion furnace.
Semiconductor diffusion furnaces often operate at a temperature in the range of twelve hundred degrees Centigrade. A semiconductor generally includes a quartz tube placed inside heating elements. The quartz tube is used as the processing chamber.
After a period of time of processing wafers at a temperature of twelve hundred degrees Centigrade, the quartz robe can begin to soften. In some cases the top of the quartz tube will sag due to the softening and gravity. As time goes on the sagging tube may hit the top of silicon wafers that are being processed in the system. When this happens, it may cause some of the silicon wafers to break and may cause down time for the diffusion furnace.
It is desirable, therefore, to replace the quartz tube periodically. However, the period of time it takes for a quartz robe to sag varies based on the operating temperature of the semiconductor diffusion furnace and differences in quartz tubes.